擲兩次骰子,你通過探索,能得出哪些事件發(fā)生的概率,寫出至少6種情況.
分析:列舉出所有情況,看點(diǎn)數(shù)和為9,點(diǎn)數(shù)和為8,點(diǎn)數(shù)和為7,點(diǎn)數(shù)和為5,點(diǎn)數(shù)和為奇數(shù),點(diǎn)數(shù)和為偶數(shù),點(diǎn)數(shù)和小于5的數(shù)情況數(shù)占總情況數(shù)的多少即可.
解答:解:
共有36種情況.
(1,6) |
(2,6) |
(3,6) |
(4,6) |
(5,6) |
(6,6) |
(1,5) |
(2,5) |
(3,5) |
(4,5) |
(5,5) |
(6,5) |
(1,4) |
(2,4) |
(3,4) |
(4,4) |
(5,4) |
(6,4) |
(1,3) |
(2,3) |
(3,3) |
(4,3) |
(5,3) |
(6,3) |
(1,2) |
(2,2) |
(3,2) |
(4,2) |
(5,2) |
(6,2) |
(1,1) |
(2,1) |
(3,1) |
(4,1) |
(5,1) |
(6,1) |
(1)點(diǎn)數(shù)和為9的情況數(shù)有4種情況,所以點(diǎn)數(shù)和為9的概率為:
;
(2)點(diǎn)數(shù)和為8的情況數(shù)有5種,所以概率為:
;
(3)點(diǎn)數(shù)和為5的情況數(shù)有4種,所以概率為:
=
;
(4)點(diǎn)數(shù)和為奇數(shù)的情況數(shù)有18種,所以概率為:
;
(5)點(diǎn)數(shù)和為偶數(shù)的情況數(shù)有18種,所以概率為:
;
(5)點(diǎn)數(shù)和小于5的情況數(shù)有6種,所以概率為:
.
點(diǎn)評:考查用列表格的方法解決概率問題;用到的知識點(diǎn)為:概率等于所求情況數(shù)與總情況數(shù)之比.